In the semiconductor industry, repair or fuse elements are a commonly used feature in integrated circuits (ICs) for improving manufacturing yield. By designing redundant circuitry into an IC and replacing defective circuits on the IC with the redundant circuits, manufacturing yields may be significantly increased. A typical process may include a test for functionality, if a defect or a fault is observed; the circuit path using the defective area is repaired. That is, the original circuit path with the fault is taken out of the circuitry by, for example, blowing a fuse and a redundant circuit path is opened. The fuses are selectively blown, for example, by passing an electrical current of a sufficient magnitude to cause the electromigration, melting, or blowing a transistor. The defective circuit path is thus effectively eliminated by creating a more resistive path or an open circuit. A fuse disconnected by a laser beam is referred to as a laser fuse, while a fuse disconnected by passing an electrical current or blowing may be referred to as a hard repair. Another method of repair is to reprogram the address of the fault with the address of the redundant circuit. This method may be termed a soft repair.
In either case, the process for running the diagnostics for uncovering fault locations and repairing them is typically limited to the test and repair process areas of a manufacturing facility. Once the IC is shipped, the capability for detailed diagnostics and repair is typically lost. Once an IC is deployed to the end user, the testing module, and repair module are not available to technicians or users of the systems in which the IC is incorporated. The test mode is tied off. This may cause field repair to be expensive and time-consuming. Therefore, while it is beneficial for a newly developed device type to have significant redundancy built into the design, as the device process matures and stabilizes, the redundancy on each IC is less used and may be considered a waste of valuable IC space.
Currently, if repair in the field is critical, field test modules designed for IC diagnostics in the field may be added to the IC. In some cases, the test diagnostics and the field diagnostics may be similar and the built in self test (BIST) modules may be redundant. Thus, the additional space on the IC is wasted.
What is needed then, is a new method and structure for self repair of semiconductor devices during post production that overcomes the above described shortcomings in the prior art.